Comment by SackSolStr
4 months ago
yes 7% ROI if no depreciation, but neither panels nor inverter are expected to last much beyond ten years. I was actually chatting with him just now since I got into this discussion, and he said he also needs a maintenance/emergency callout and cleaning contract, thats about €250 a year. In spite of this, he was still happy with doing this, good for the planet, even if not for this wallet. He also put up a large screen with the relevant numbers to train others in the house to use appliances at optimal times.
Panels are normally warranted not to drop below 80% of rated output after 25 or 30 years, although some are defective and crack within a year or so. But they don't start dropping off more rapidly at that point; rather, their output declines more slowly after that point. Those panels will be fine 50 years from now if he doesn't throw them away.
Inverters are a different problem, and they do in fact die after a few years. But you don't need the inverter to use the energy.